The Research Core will be directed by Dr. Caren Gundberg. This Core will provide direct skeletal analysis and biochemical measurements of bone and mineral metabolism as to facilitate CORT basic and translational research projects. The Core will partner with the Physiology Core of the Yale Core Center for Musculoskeletal Diseases, and allow for the necessary expansion of services in order to provide the dedicated support of CORT projects. Specific services offered will include: 1. Fixation, embedding, sectioning, and slide preparation of undecalcified skeletal tissue. 2. Specialized staining of bone from animal models, including toluidine blue, von Kossa, Safronin O, alkaline phosphatase as well as specific immunohistochemical localizations and TUNEL assays. 3. Measurement and interpretation of standard static and dynamic parameters of bone histomorphometrical analysis. 4. Assessment of mineralizing cells in culture. Analyses will include both alizarin red and von Kossa staining of mineralizing cultures as well as direct measurement of calcium and phosphorus content, alkaline phosphatase and osteocalcin. 5. Measurement of PTH (intact and mid-molecule), FGF23 (intact and C-terminal), 25(OH)D, 1,25(OH)2D, serum PINP, human osteocalcin, C-telopeptide of type I collagen (Crosslaps) and urinary minerals and creatinine will be provided for human studies. 6. Measurement of mouse PTH, FGF23 (intact), 25(OH)D, and 1,25(OH)2D, mouse osteocalcin, Ctelopeptide of type I collagen (Ratlaps), and urinary minerals will be provided for human studies.